Caged fasteners such as caged nuts are frequently used in the manufacture of automobiles and other vehicles. A caged nut provides advantages in that it can be assembled into a product framework during manufacture, so that the number of operations required in the final assembly of the product are reduced. In addition, a caged nut can be attached to the framework in locations which subsequently become enclosed or tightly circumscribed as more parts are assembled onto the product. If a caged nut was not provided in such situations, it would be very difficult to locate a nut by hand to receive a bolt used to fasten components such as an engine cradle onto a vehicle frame.
A caged nut generally comprises a nut encaged in a structure, known as a retainer, that allows access to the nut bore, and provides the nut with a limited range of movement within the retainer. The range of motion of the nut in the cage is provided so that the part being mounted on the frame may be adjusted relative to the frame during final assembly. In the manufacture of automobiles using caged nuts, the retainer was traditionally welded onto the frame of the automobile and provided a nut at a selected location for the attachment of another part, such as an engine cradle, to the frame.
Welding the retainer to the frame suffered from a number of disadvantages, however, one of which being that the welding operation promoted corrosion of the frame. For this reason, other means of attaching the retainer to the frame have been developed.
U.S. Pat. No. 5,624,319 to Golczyk et al. discloses a two-part cage nut 20 having a nut portion 2 and a holding part comprising a slide plate 5 and a clamping arm 6. The clamping arm 6 is formed to extend parallel with the slide plate 5 to provide a generally C-shaped profile, which can be clipped onto a carrier plate 10.
U.S. Pat. No. 4,762,451 to Collins discloses a caged nut 1 which includes lugs 4, through which pass apertures 5. Nut 1 can be secured either to a separate cage which can then be welded to a sheet metal support panel 10 or to the support panel 10 itself, by return bent legs 11 which pass through apertures 5 and are bent to secure nut 1 in place.
U.S. Pat. No. 4,875,816 to Peterson discloses a caged fastener 10 for mounting within a hollow frame member 60. Caged fastener 10 comprises a fastener body 12 and a cage 30 having spring member 52, rigid members 54, secondary spring members 56 and lateral struts 57. Spring member 52, rigid members 54, secondary spring members 56 and lateral struts 57 are all sized and shaped to fit within a nut chamber 66 in frame member 60, and to frictionally hold caged fastener 10 therein.
U.S. Pat. No. 5,193,643 to McIntyre discloses a nut and retainer assembly 42, 44 which comprises a nut 50 and a retainer 52, 108. Retainer 52, 108 includes spring biased tabs 70, 110 and a handle portions 72, 112 for locking nut and retainer assembly 42, 44 within a housing 16 or hollow frame 14.
A disadvantage of all of the prior art patents discussed above is that none of them make any provision for the effects of a collision. It is well known in the automotive industry that in a crash, particularly in a head-on crash, it is desirable to provide "crumple zones" which allow the vehicle frame to crumple accordion-style, thereby absorbing some of the forces caused by the crash so as to protect the vehicle passengers. However, when the vehicle engine cradle is rigidly mounted to the frame, this crumpling may cause the engine to be forced rearward into the passenger compartment, which is of course undesirable as severe injuries to the passengers may result. Although the prior art patents discussed above allow for some limited planar movement of the nut relative to the retainer so that a bolt may be inserted into the nut more easily, the planar movement is limited to a small fraction of an inch, which does very little or nothing to inhibit the engine from being forced rearward.
What is desired therefore is a caged nut assembly which can be mounted to a frame member without welding, which does not promote corrosion on a frame when mounted thereon, which allows for planar movement of the nut relative to the retainer so that a bolt may be inserted into the nut more easily, and which allows for movement of the entire caged nut assembly relative to the frame during a collision to inhibit the engine cradle from being forced into the passenger compartment while the frame crumples.